- Open Access
Pathogenic infection of Macaca nemestrinawith a CCR5-tropic subtype-C simian-human immunodeficiency virus
© Ho et al; licensee BioMed Central Ltd. 2009
- Received: 28 April 2009
- Accepted: 14 July 2009
- Published: 14 July 2009
Although pig-tailed macaques (Macaca nemestrina) have been used in AIDS research for years, less is known about the early immunopathogenic events in this species, as compared to rhesus macaques (Macaca mulatta). Similarly, the events in early infection are well-characterized for simian immunodeficiency viruses (SIV), but less so for chimeric simian-human immunodeficiency viruses (SHIV), although the latter have been widely used in HIV vaccine studies. Here, we report the consequences of intrarectal infection with a CCR5-tropic clade C SHIV-1157ipd3N4 in pig-tailed macaques.
Plasma and cell-associated virus was detectable in peripheral blood and intestinal tissues of all four pig-tailed macaques following intrarectal inoculation with SHIV-1157ipd3N4. We also observed a rapid and irreversible loss of CD4+ T cells at multiple mucosal sites, resulting in a marked decrease of CD4:CD8 T cell ratios 0.5–4 weeks after inoculation. This depletion targeted subsets of CD4+ T cells expressing the CCR5 coreceptor and having a CD28-CD95+ effector memory phenotype, consistent with the R5-tropism of SHIV-1157ipd3N4. All three animals that were studied beyond the acute phase seroconverted as early as week 4, with two developing cross-clade neutralizing antibody responses by week 24. These two animals also demonstrated persistent plasma viremia for >48 weeks. One of these animals developed AIDS, as shown by peripheral blood CD4+ T-cell depletion starting at 20 weeks post inoculation.
These findings indicate that SHIV-1157ipd3N4-induced pathogenesis in pig-tailed macaques followed a similar course as SIV-infected rhesus macaques. Thus, R5 SHIV-C-infection of pig-tailed macaques could provide a useful and relevant model for AIDS vaccine and pathogenesis research.
- Rhesus Macaque
- Simian Immunodeficiency Virus
- Simian Immunodeficiency Virus
- Simian Immunodeficiency Virus Infection
- Intrarectal Inoculation
The research of AIDS pathogenesis has been facilitated by the use of Asian macaques known to develop AIDS-like diseases from lentivirus infection, including rhesus (M. mulatta), cynomolgus (M. fascicularis), and pig-tailed (M. nemestrina) macaques [1–11]. Studies in rhesus macaques have provided extensive insight into the biology of disease-susceptible animals to advance ongoing efforts towards developing an effective human AIDS vaccine. On the other hand, much less is known about the early events after lentiviral infection in other macaque species, including pig-tailed macaques.
The species/subspecies of macaques used in a study can be a significant determinant of viral infectivity and disease susceptibility. For example, in a comparative study of Asian macaques infected intravenously with simian immunodeficiency virus (SIV) or simian-human immunodeficiency virus (SHIV) strains, SIVmac251 or SHIV89.6P, Reimann et al. found lower plasma viral loads, higher levels of peripheral CD4+ T cells, and higher survival rates in cynomolgus and Chinese rhesus, compared to similarly infected Indian rhesus . Interestingly, ten Haaft et al. reported contrasting findings in cynomolgus vs. Indian rhesus infected intravenously or via select mucosal routes . Their study showed that while cynomolgus macaques had lower steady-state viral loads after SIV infection, there was no such difference after SHIV89.6P infection. Consistent with the Reimann et al. report above, Ling et al. also showed a differential response to lentiviral infection at the subspecies level. Compared to their Indian counterparts, Chinese rhesus infected with SIVmac239 had lower plasma viral loads in acute infection, maintained lower setpoint plasma viremia, and experienced less severe depletion of intestinal CD4+ effector cells, all of which resulted in better clinical outcomes . However, Burdo et al. found that serial passage of SIVmac128 in Chinese rhesus resulted in increased steady-state viral loads as compared to animals infected with the virus derived from Indian monkeys, implying that host adaptation plays an important role in viral fitness and pathogenicity .
Taken together, these findings suggest that the efforts to develop an AIDS vaccine may be well served by examining a diverse range of antiviral responses and disease susceptibilities in different animal models. Pig-tailed macaques are of particular interest for several reasons. First, despite sharing a common ancestor, pig-tailed macaques are more distantly related to cynomolgus and rhesus macaques than the latter species are to each other [16, 17]. This evolutionary distance may have genetic implications affecting components of the adaptive immune response, including T-cell receptor diversity and major histocompatibility complex (MHC) molecules [18, 19]. Second, pig-tailed macaques are defective in a restriction factor TRIM5α  used by rhesus macaques to inhibit replication by certain retroviruses, such as HIV-1 . Pig-tailed macaques have previously been shown to be susceptible to infection by HIV-1 [22, 23] and recently, by simian-tropic (st)HIV-1 strains . Third, evidence exists indicating that pig-tails are more susceptible to lentivirus-induced disease. In a comparative study of pig-tailed and rhesus macaques infected with SHIVSF162P4, Polacino et al. found higher peak and setpoint viral loads in pig-tailed macaques despite similar infectivity between the two species, demonstrating that pig-tails were less able to control infection . This finding was consistent with an early report by Rosenberg et al., who found that SIVPBj-14-infected pig-tailed macaques were more susceptible to death resulting from gastrointestinal distress than their rhesus counterparts . Similarly, other studies have documented persistent infection, CD4+ T cell depletion, and/or development of AIDS-like diseases in pig-tails, but not rhesus, infected with HIV-2 primary isolates [27–29]. Thus, based on their increased susceptibility to HIV infection and to lentivirus-induced disease, compared to rhesus, pig-tailed macaques may be a useful animal model for addressing the diverse responses to HIV-1 infection in humans.
Elucidation of the immunopathogenic events in mucosa-associated lymphoid tissue (MALT) has been a major advance in AIDS research in the last ten years [30, 31]. Dramatic and irreversible depletion of CD4+ T cells at multiple mucosal sites occurs early after SIV infection [32–42]. Furthermore, the virus specifically targets CCR5+ and activated memory CD4+ T-cells [35, 37, 40–45] comprising the majority of total lymphocytes found in MALT, especially in the intestine, the largest immunologic organ in the body [46, 47]. In contrast, these subsets represent small numbers of circulating CD4+ lymphocytes in blood, lymph nodes, and other secondary lymphoid tissues. Consequently, depletion of CD4+ T cells in these tissues is not as dramatic as in the mucosal compartment during acute infection [32, 35, 37–39, 42, 48]. Thus, monitoring mucosal CD4+ T cells may provide important insight into lentivirus-induced immunopathogenesis. However, compared to the extensive knowledge accumulated from rhesus studies, less is known about mucosal pathogenic events in pig-tailed macaques during early infection.
The rapid depletion of CD4+ T cells observed in the MALT of SIV-infected macaques contrasts with the depletion observed in peripheral blood of macaques infected with the first-generation of SHIVs, such as SHIV-HXBc2 and SHIV89.6P. This discrepancy most likely reflects the CXCR4-tropism of these SHIVs vs. the CCR5-tropism of SIV [49, 50]. As most of the transmitted viruses in sexual and maternal-infant HIV-1 infection are CCR5-tropic, the use of R5 SHIVs may be more biologically relevant in preclinical vaccine studies . Furthermore, currently available SHIVs are predominantly derived from subtype B isolates of HIV-1 [52–57], whereas the majority of global infections results from subtype C virus transmission . Recently, Song et al. reported the construction of a CCR5-tropic subtype C SHIV-1157ipd3N4 (also referred to as SHIV-C for short), which has been shown to be highly replication-competent and mucosally transmissible in Indian- and Chinese-origin rhesus macaques . Three of five rhesus infected with parental versions of SHIV-1157ipd3N4 progressed to AIDS within 2–5 years postexposure . Two of the 13 rhesus monkeys infected with SHIV-1157ipd3N4 also progressed to AIDS within 80–100 weeks (Chenine et al., unpublished data). This pathogenic R5-tropic SHIV-C may therefore represent an important tool for pathogenesis study of primate lentiviruses and preclinical evaluation of candidate HIV vaccines. In the present study, we evaluated the infectivity and pathogenicity of SHIV-1157ipd3N4 in pig-tailed macaques to determine its potential role as an alternative challenge model in future AIDS vaccine studies.
SHIV-1157ipd3N4 infection in pig-tailed macaques
The fact that all four pig-tailed macaques became infected after inoculation with SHIV-1157ipd3N4 confirmed the susceptibility of this species to infection by this virus, which was propagated and studied only in rhesus monkeys . Peak viral loads from the four infected pig-tailed macaques approached the lower range reported for Indian rhesus, and within the range for Chinese rhesus  (Fig. 1A). Plasma virus also peaked at the same time in both species (2 weeks p.i.). Viremia persisted in 2/3 pig-tails during the year-long study, similar to results reported for rhesus monkeys (3/5 and 3/8, respectively, for Chinese and Indian rhesus)  (Fig. 1A).
Early and severe SHIV-1157ipd3N4-induced mucosal immunopathogenesis
The severe loss of CD3+CD4+ T cells was also found in other mucosal tissues, including the colon and the lung, the latter accessible by bronchoalveolar lavage (BAL) sampling (Fig. 2B). Similar to the duodenum, depletion of CD4+ T cells was not observed in the colon at week 1 p.i. in two macaques (data not shown). By week 4 p.i., CD4+ T-cell levels had decreased from 43.4% to 9.2%, or 79% from pre-existing levels in macaque L03165. The elimination of CD4+ T lymphocytes was more severe and rapid in lung mucosa, where CD3+CD4+ T cells were undetectable by 3 days p.i. In fact, BAL CD4+ T cells remained at undetectable or nearly undetectable levels for 1–2 weeks after virus inoculation in two macaques (Fig. 2B; and data not shown). However, in at least one macaque (L03165), the percentage of CD3+CD4+ T cells in the BAL returned to pre-inoculation levels by week 20 p.i. (Fig. 2B).
As a result of the profound depletion of CD4+ T cells in the mucosal tissues, we observed a striking decrease of CD4:CD8 T cell ratios during acute infection (Fig. 2C). By 2–4 weeks p.i., the T-cell ratios in the duodenum had decreased nearly 23-fold, from a pre-inoculation range of 0.47–0.74 to a post-inoculation range of 0.016–0.037. The decrease in the duodenal T-cell ratios largely persisted throughout the course of infection, with recovery in CD3+CD4+ T-cell levels resulting in only minimal increases in the CD4:CD8 ratios, which did not exceed 0.18. In macaque L03165, the massive elimination of BAL CD4+ T cells as early as 3 days p.i. resulted in a marked decrease of CD4:CD8 T-cell ratios up to 2 weeks p.i., dropping from a pre-inoculation ratio of 0.43 to a range of 0–0.003 after infection (data not shown).
To our knowledge, this is the first report of a prospective analysis of the immunopathogenesis in multiple mucosal compartments during infection with a R5 SHIV in pig-tailed macaques. Chen et al. found that pig-tailed macaques infected with a R5-tropic clade C SHIVCHN19P4 were significantly depleted of jejunal CD4+ T cells at 2 weeks p.i., with no remarkable change in immune activation or proliferation of CD4+ gut lymphocytes, as measured by CD25 and Ki67 staining, respectively [60, 61]. Chase et al. reported that ileal CCR5+CD4+ T cells of pig-tails inoculated with an immunosuppressive viral strain SIV/ΔB670 together with a macrophage-tropic molecular clone SIV/17E-Fr dropped from average uninfected levels of 44% to 8% by 2 weeks p.i. . A significant decrease in CD25hi cells and an increase in Ki67+ cells were also observed in CD4+ gut lymphocytes from the SIV-infected animals . Our data confirm and extend these previous findings that gut immunopathogenesis is a hallmark of early R5-tropic SIV/SHIV infection in pig-tailed macaques.
The results reported here also indicate that R5 SHIV-C-induced mucosal pathogenesis in pig-tails followed a similar course as described in SIV-infected rhesus. These studies demonstrated profound CD4+ T-cell losses, nearly complete in some cases, by days 10–21 after infection [32–42]. There is no discernable difference in the depletion of CD4+ T lymphocytes within intestinal and lung mucosa in pig-tails, with regard to the kinetics or severity of the depletion, compared to these previous reports in rhesus. Notably, the elimination of mucosal CD4+ T cells in pig-tailed macaques was often followed by the partial or limited return of these populations over the course of the study period (Fig. 2A–B). In fact, the partial recovery of CD4+ T cells in the gut of SIVmac251-infected rhesus macaques has been documented by Veazey et al., who showed intestinal CD3+CD4+ T cells increased up to 20% by week 5 p.i. in a few infected animals . Similarly, Okoye et al. reported that BAL CD4+ T-cell levels from SIVmac239-infected rhesus initially recovered after early depletion up to approximately 14 weeks p.i., then decreased progressively thereafter . The mechanism underlying the recovery of mucosal CD4+ T cells after acute infection remains to be defined, although there is evidence identifying the majority of repopulating intestinal CD4+ T cells as naïve [40, 42]. While the rebound of mucosal CD4+ T cells appeared to be partial and/or transient, depletion of this cell population in early SHIV infection was sustained during the course of infection (Fig. 2A–B). Moreover, peak infection of intestinal mononuclear cells at 1.5–2 weeks p.i. coincided with the onset of CD4+ T-cell depletion, consistent with previous findings [33, 35, 38, 39, 44, 46, 61, 64, 65] (Figs. 1C and 2A). Thus, the availability of target cells is a critical determinant of mucosal immunopathogenesis.
Acute SHIV-1157ipd3N4 infection results in specific elimination of mucosal CCR5+ and effector memory CD4+T lymphocytes
A substantial reduction of CD4+ effector memory T cells (TEM), identified by their CD28-CD95+ phenotype, was also seen in the duodenum of all four infected pig-tails. By 2–4 weeks p.i., these numbers fell from 33.2% to 0% in J02185; 75.6% to 3.6% in K03135; 22.2% to 8.6% in L03165; and 21.9% to 7.4% in M04123 (Fig. 3B). On average, CD4+ TEM dropped from 38.2% to 4.9% (standard deviation of 25.5% and 3.9%, respectively), reflecting an 80.7 ± 19.7% decrease of pre-existing populations. CD4+ TEM cells were undetectable by flow cytometry at 2 weeks p.i. in macaque J02185, the same animal whose CD4+ T cells were 97% depleted by week 4 p.i. (Figs. 2A and 3B). By 20–24 weeks p.i., the numbers of CD4+ TEM in all three macaques followed beyond the acute phase had recovered to 62.4 ± 11.3% of their pre-inoculation levels, despite only a 28% recovery in total CD4+ T cells (Figs. 2A and 3B). The coincident increase of central memory CD4+ T cells (TCM) beginning at 2 weeks p.i., when the effector memory subset was profoundly depleted (Fig. 3C), suggests a homeostatic mechanism whereby the TEM are derived from the proliferation and differentiation of the TCM population . Thereafter, TCM levels reached a plateau in all three animals until week 12 p.i., at which time this cell population decreased in K03135.
Our results indicate that SHIV-1157ipd3N4 induced a similar immunopathogenesis in pig-tails as SIV in rhesus, based on the R5-tropism of both viruses. Rhesus macaques showed a dramatic decline of mucosal CD4+ T cells with a CCR5+ memory phenotype at 11–28 days following infection [35, 37, 40–45] The specific targeting of mucosal CCR5 and effector memory CD4+ T cell subsets is consistent with the elevated levels of CCR5 on activated memory T cells [32, 46, 47], and the predominance of an activated/memory phenotype in mucosal tissue [30, 31]. In fact, rhesus studies have reported that large numbers of CCR5+ target cells reside at mucosal sites, including the gut and lung, where approximately 50–90% of CD4+ T cells express CCR5 [30–32, 35, 40, 41, 44, 66]. We found comparable levels of CCR5+CD4+ T cells in our analysis of mucosal tissues from uninfected pig-tailed macaques, including the duodenum (79 ± 9%), colon (63 ± 10%), and BAL (98 ± 0.4%), the latter reported for two of four animals. Therefore, as reported in SIV-infected rhesus, the mucosa provides a critical reservoir of CD4+ target cells for R5-specific SHIV-C infection in pig-tails as demonstrated by the sharp decrease of CCR5+ and TEM cells by 2 weeks p.i (Fig. 3A–B).
The basis for the apparent increase of intestinal CCR5+ and TEM cells after initial depletion (Fig. 3A–B) is not well understood. As the percentages of the subsets are based on total CD4+ T numbers, it follows that proportional increases in CCR5+ and TEM cells concurrent with severe CD4+ T-cell losses during acute and chronic infection (Fig. 2A) may result in the apparent "recovery" of the subset populations . Further, Veazey et al. observed at 2 weeks p.i. that more than 50% of the residual intestinal CD4+ T cells in a few SIV-infected rhesus were CCR5+ and naive (CD45RAHI) . At 4–6 months p.i. most residual CD4+ T cells in the gut were naïve, but lacked CCR5 expression . Thus, while it is possible that the "recovery" of CCR5+ and memory subsets may represent actual residual cells which remained and expanded, these populations may also be derived from naive cells newly formed and recruited to the mucosa early after infection [40, 42].
Loss of specific CD4+T cell subsets during acute SHIV-1157ipd3N4 infection also occurs in peripheral blood
We also observed decreases in the absolute counts of CCR5+ and CD28-CD95+ subsets in peripheral blood CD4+ T cells from all four pig-tailed macaques in early R5 SHIV-C infection (Fig. 4B–C). By 2–3 weeks p.i., CCR5-expressing T cells dropped from 15.2 to 6.2 cells/μl (standard deviation of 4.1 and 2.3 cells/μl, respectively), or 56.9 ± 21.6% from pre-challenge levels (Fig. 4B). Similarly, CD4+ TEM fell from 32.9 to 13.1 cells/μl (standard deviation of 12.5 and 4.4 cells/μl, respectively), reflecting a loss of 58 ± 13.7% in this population (Fig. 4C). However, compared to the duodenum, substantially lower levels of these subsets were found in the peripheral blood of uninfected pig-tails (for CCR5+, 79 ± 9% vs. 2.8 ± 0.3%; for CD28-CD95+, 38.2 ± 25.5% vs. 4.5 ± 1.7%) (Fig. 3A–B; and data not shown). Similarly low levels of peripheral blood CD4+ T cells expressing CCR5 and having an effector memory phenotype (approximately 3–16%) have been reported in rhesus macaques [30, 31, 35, 40, 41, 66]. Thus, consistent with previous findings in rhesus, the small numbers of pre-existing peripheral CCR5+ and TEM cells in pig-tailed macaques precluded dramatic changes to the total absolute CD4+ T-cell count, despite substantial losses to the population subsets due to SHIV-C infection (Fig. 4).
Findings reported here demonstrate the pathogenic potential of SHIV-1157ipd3N4 infection in pig-tailed macaques. The differential clinical responses in J02185, K03135, and L03165 (Figs. 1A, C, and 4A) suggest a spectrum of disease courses is possible from SHIV-C infections, consistent with previous findings in SIV and R5 SHIV strains, and the outbred nature of the animals studied. Peripheral lymphopenia and AIDS-defining events have also been documented in an Indian rhesus infected with SHIV-1157ipd, a late-stage biological isolate from which SHIV-1157ipd3N4 was directly derived [58, 59]. Additionally, long-term monitoring of SHIV-1157ipd3N4 infection in rhesus has shown AIDS progression in two animals (Chenine et al., unpublished data). Song et al. reported relatively stable absolute peripheral CD4+ T-cell counts in all Indian- and Chinese-origin rhesus acutely infected with SHIV-1157ipd3N4 and followed for 12 weeks . They also found that 43–66% of peripheral CD4+ TCM was depleted in two of five Indian rhesus at 8 weeks p.i. Compared to pre-existing levels at week 0, we found a similar 39–59% decrease of peripheral CD4+ TCM in pig-tails at 2 weeks p.i.; by 8 weeks p.i., this decrease was 5–28%, reflecting the partial recovery of these cells in blood (data not shown). Interestingly, we observed an association between low pre-inoculation counts of peripheral CD4+ TCM and progression to SHIV-C-induced disease in one animal (K03135) (data not shown), consistent with previous findings in SIVmac251-infected pig-tailed macaques . Rhesus monkeys infected with another pathogenic R5 SHIV-C, SHIV-2873Nip, which was constructed from the backbone of SHIV-1157ipd3N4, also demonstrated a loss of peripheral CD4+ memory T cells, along with depletion of gut CD4+ T lymphocytes .
Antibody-mediated immune responses to SHIV-1157ipd3N4 infection
Serum neutralizing antibody response in pig-tailed macaques 36 weeks post-inoculation with SHIV-1157ipd3N4.
Q461d1 (A) a
Clade C Human
Our prospective analysis of SHIV-1157idp3N4-infected animals with emphasis on early acute infection demonstrates that R5 SHIV-C-induced pathogenesis in pig-tailed macaques parallel findings in CCR5-tropic SIV/SHIV rhesus models. Findings reported here support the value of pig-tailed macaques as a relevant animal model for the study of lentiviral pathogenesis and preclinical AIDS vaccines.
Four juvenile pig-tailed macaques (M. nemestrina), all negative for simian type D retrovirus by serology and polymerase chain reaction (PCR), were used in this study. Animals were inoculated intrarectally, and tissue samples were collected at specific timepoints pre- and post-inoculation for prospective monitoring of viral loads, T-cell subsets, blood chemistry, and antibody responses. General health of the animals, including body weight and temperature, was monitored by routine examinations. All animals were cared for in accordance with established National Institutes of Health guidelines, and the experimental procedures were performed with the approval of the Institutional Animal Care and Use Committee at the University of Washington.
The derivation of SHIV-1157ipd3N4 was described by Song et al. . A rhesus PBMC-grown stock was used for this study. All animals received 1 ml of undiluted SHIV-1157ipd3N4 by an atraumatic intrarectal inoculation. The virus stock had a p27 concentration of 95 ng/ml and an in vitro infectivity as determined by 50% tissue culture infectious doses (TCID50) of 106 per ml as titrated in TZM-bl cells (R. Song, personal communication).
TZM-bl cells (also called JC53-bl, clone 13) were contributed by John Kappes and Xiaoyun Wu and obtained from the National Institutes of Health (NIH) AIDS Reference Reagent Repository Program (catalog no. 8129) . Cells were cultured in Dulbecco modified Eagle medium supplemented with 10% fetal bovine serum (FBS) and 2 mM glutamine.
Tissue collection and isolation of lymphocytes
Peripheral blood was drawn by venipuncture into EDTA or SST tubes for extraction of plasma and PBMC, or serum, respectively. BAL samples were obtained by laryngoscope-aided introduction of a 5 mm video bronchoscope through the mouth and into the trachea. Lavage with 3–5 separate 10-ml aliquots of sterile saline was performed by injecting the saline into a terminal bronchiole, after which the saline infusate was aspirated with continuous flow vacuum at approximately 90–100 mm Hg of negative pressure. For endoscope-guided pinch biopsies obtained from the duodenum or colon, an 8.9 mm diameter video gastroscope (Karl Storz Veterinary Endoscopy, Goleta, CA) was inserted as far as the distal duodenum/proximal jejunum (90–130 cm from the mouth), or into the descending/transverse colon (50–70 cm from the anus), respectively. A maximum of 23 pinch biopsies (about 1 mm3) was collected via the gastroscope with sterile 2.0 mm biopsy forceps.
EDTA-treated blood was subjected to Lymphoprep (Ficoll) density gradient centrifugation for isolation of viable PBMC, or stained by a whole blood lysis technique as described below. BAL samples were centrifuged to pellet cells, but enrichment of lymphocytes was not performed. Biopsies were pooled from the duodenum or colon, treated with 5 mM EDTA and 60 U/ml collagenase, and isolated cells were enriched for lymphocytes by Percoll density gradient centrifugation, as previously described [40, 42]. Viability of intestinal lymphocytes averaged 88 ± 4%, as determined by trypan blue exclusion.
Plasma and cell-associated viral loads
Viral load was assayed as previously described [72, 78]. Briefly, viral RNA load in EDTA-anticoagulated, cell-free plasma was determined by real-time RT-PCR after reverse transcriptase reaction. Proviral cDNA load in total mononuclear cells from peripheral blood or duodenal biopsies was determined by real-time PCR analysis.
Cells were stained for four-color flow cytometric analysis, using antibodies directly conjugated to either fluorescein isothiocyanate (FITC), phycoerythrin (PE), peridinin chlorophyll protein (PerCP), or allophycocyanin (APC). Briefly, for whole blood staining, 1 ml of whole blood was treated with 14 ml of ammonium chloride lysis solution for 7 min, centrifuged (700 × g, 5 min), and the resultant cell pellet was resuspended in 1 ml of staining medium (RPMI supplemented with 1% FBS and 0.02% NaN3) . Fifty-μl aliquots of the cell suspension were triple-stained with CD3-FITC (SP34-2), CD4-PerCP-Cy5.5 (L200), and CD8-APC (SK1), and double-stained with CD2-FITC (S5.2) and CD20-PerCP-Cy5.5 (L27). Cells were incubated in the dark for 20 to 30 min, washed, and resuspended in 1% paraformaldehyde. For mucosal and peripheral blood lymphocytes, cells were stained by incubating 1–5 × 105 cells with combinations of monoclonal antibodies at 4°C for 30 min, washed, and then fixed in 2% paraformaldehyde. Monoclonal antibodies used were: CD3-FITC (SP34), CD3-PerCP (SP34-2), CD4-APC (L200), CD8-PerCP (SK1), CD8-APC (SK1), CCR5-PE (3A9), CD28-PE (CD28.2), and CD95-FITC (DX2). All antibodies were purchased from Becton Dickinson Biosciences (San Jose, CA). Controls included appropriate unstained, fluorescence-minus-one (FMO)-stained, and single-color-stained, samples, for compensation and gating. Data were acquired on a FACSCalibur flow cytometer (Becton Dickinson Immunocytometry Systems), where 10,000–20,000 gated lymphocyte events were collected, and analyzed with FlowJo software (Version 7.1.3, Tree Star, Ashland, OR). The absolute numbers of CD3+CD4+ lymphocytes were determined using flow cytometry analysis software according to guidelines from the Centers for Disease Control and Prevention for T-cell determinations in HIV-infected individuals .
Enzyme-linked immunosorbent assay (ELISA)
The titers of whole virus SIVmac- and HIV-1SF162 gp120-specific antibodies were measured by ELISA as previously described . Endpoint titers were determined as the reciprocal of the highest serum dilution that resulted in an optical density reading greater than the average values obtained with negative macaque sera plus three standard deviations.
The neutralization activity of sera from SHIV-1157ipd3N4-inoculated pig-tailed macaques was measured in a pseudotyped virus assay as described . Indicator viruses with envelope derived from the following HIV-1 were used: subtype A isolate Q461d1 ; subtype B isolates SF162, SS1196.1, 89.6, QH0692.42, and SC422661.8 [72, 74]; and subtype C isolate 1084i . All assay stocks were titrated in TZM-bl cells as described previously [72, 74]. Indicator virus containing 150 TCID50 was incubated with serial dilutions of serum samples (starting at 1:30) in triplicate in a total volume of 60 μl for 1.5 hr at 37°C in 96-well U-bottom tissue culture plates (Corning). TZM-bl cells plated 24 hr previously (3,000 cells in 100 μl of growth medium) were treated with 2 μg/ml polybrene for 30 min at 37°C. One set of control wells received cells plus virus (virus control), and another set received cells only (background control). After a 72-hr incubation, luciferase activities were analyzed using BrightGlo substrate solution as described by the supplier (Promega). Neutralization activity was expressed as the highest serum dilution that resulted in 50% reduction of relative luciferase units (RLU). Values obtained with pre-inoculation sera were subtracted from those obtained with post-inoculation sera for each animal.
We thank the veterinary and animal care staff at the WaNPRC for excellent care of the macaques; Drs. Steve Kelley and Keith Vogel, and Leon Flanary and Joel Ahrens for mucosal sample collections; Dr. Robert Murnane for histopathological analyses; Heather Mack, Ryan Wallerstedt, Valerie Teske, Xuebing Li, Taryn Urion, and Modou Mbowe for expert technical assistance; and Drs. Don Sodora, Ron Veazey, Louis Picker, and John Fanton, and Kiran Mir and Amanda Leone for helpful discussions. This study is supported in part by NIH grants and contracts P51 RR0166 (WaNPRC) and P01 AI24048 (RMR and SLH).
- Batten CJ, De Rose R, Wilson KM, Agy MB, Chea S, Stratov I, Montefiori DC, Kent SJ: Comparative evaluation of simian, simian-human, and human immunodeficiency virus infections in the pigtail macaque (Macaca nemestrina) model. AIDS Res Hum Retroviruses. 2006, 22: 580-588. 10.1089/aid.2006.22.580.View ArticlePubMedGoogle Scholar
- Dewhurst S, Embretson JE, Anderson DC, Mullins JI, Fultz PN: Sequence analysis and acute pathogenicity of molecularly cloned SIVSMM-PBj14. Nature. 1990, 345: 636-640. 10.1038/345636a0.View ArticlePubMedGoogle Scholar
- Haigwood NL: Predictive values of primate models for AIDS. AIDS Rev. 2004, 6: 187-198.PubMedGoogle Scholar
- Hu S-L: Non-human primate models for AIDS vaccine research. Curr Drug Targets Infect Disord. 2005, 5: 193-201. 10.2174/1568005054201508.PubMed CentralView ArticlePubMedGoogle Scholar
- Israel ZR, Dean GA, Maul DH, O'Neil SP, Dreitz MJ, Mullins JI, Fultz PN, Hoover EA: Early pathogenesis of disease caused by SIVsmmPBj14 molecular clone 1.9 in macaques. AIDS Res Hum Retroviruses. 1993, 9: 277-286. 10.1089/aid.1993.9.277.View ArticlePubMedGoogle Scholar
- Joag SV, Li Z, Foresman L, Stephens EB, Zhao LJ, Adany I, Pinson DM, McClure HM, Narayan O: Chimeric simian/human immunodeficiency virus that causes progressive loss of CD4+ T cells and AIDS in pig-tailed macaques. J Virol. 1996, 70: 3189-3197.PubMed CentralPubMedGoogle Scholar
- Lackner AA, Veazey RS: Current concepts in AIDS pathogenesis: insights from the SIV/macaque model. Annu Rev Med. 2007, 58: 461-476. 10.1146/annurev.med.58.082405.094316.View ArticlePubMedGoogle Scholar
- Lifson JD, Nowak MA, Goldstein S, Rossio JL, Kinter A, Vasquez G, Wiltrout TA, Brown C, Schneider D, Wahl L, Lloyd AL, Williams J, Elkins WR, Fauci AS, Hirsch VM: The extent of early viral replication is a critical determinant of the natural history of simian immunodeficiency virus infection. J Virol. 1997, 71: 9508-9514.PubMed CentralPubMedGoogle Scholar
- Novembre FJ, De Rosayro J, O'Neil SP, Anderson DC, Klumpp SA, McClure HM: Isolation and characterization of a neuropathogenic simian immunodeficiency virus derived from a sooty mangabey. J Virol. 1998, 72: 8841-8851.PubMed CentralPubMedGoogle Scholar
- Shibata R, Igarashi T, Haigwood N, Buckler-White A, Ogert R, Ross W, Willey R, Cho MW, Martin MA: Neutralizing antibody directed against the HIV-1 envelope glycoprotein can completely block HIV-1/SIV chimeric virus infections of macaque monkeys. Nat Med. 1999, 5: 204-210. 10.1038/5568.View ArticlePubMedGoogle Scholar
- Staprans SI, Feinberg MB: The roles of nonhuman primates in the preclinical evaluation of candidate AIDS vaccines. Expert Rev Vaccines. 2004, 3: S5-32. 10.1586/14760584.3.4.S5.View ArticlePubMedGoogle Scholar
- Reimann KA, Li JT, Voss G, Lekutis C, Tenner-Racz K, Racz P, Lin W, Montefiori DC, Lee-Parritz DE, Lu Y, Collman RG, Sodroski J, Letvin NL: An env gene derived from a primary human immunodeficiency virus type 1 isolate confers high in vivo replicative capacity to a chimeric simian/human immunodeficiency virus in rhesus monkeys. J Virol. 1996, 70: 3198-3206.PubMed CentralPubMedGoogle Scholar
- ten Haaft P, Almond N, Biberfeld G, Cafaro A, Cranage M, Ensoli B, Hunsmann G, Polyanskaya N, Stahl-Hennig C, Thortensson R, Titti F, Heeney J: Comparison of early plasma RNA loads in different macaque species and the impact of different routes of exposure on SIV/SHIV infection. J Med Primatol. 2001, 30: 207-214. 10.1034/j.1600-0684.2001.d01-54.x.View ArticlePubMedGoogle Scholar
- Ling B, Veazey RS, Luckay A, Penedo C, Xu K, Lifson JD, Marx PA: SIV(mac) pathogenesis in rhesus macaques of Chinese and Indian origin compared with primary HIV infections in humans. AIDS. 2002, 16: 1489-1496. 10.1097/00002030-200207260-00005.View ArticlePubMedGoogle Scholar
- Burdo TH, Marcondes MC, Lanigan CM, Penedo MC, Fox HS: Susceptibility of Chinese rhesus monkeys to SIV infection. AIDS. 2005, 19: 1704-1706. 10.1097/01.aids.0000186823.76230.33.View ArticlePubMedGoogle Scholar
- Fooden J: Classification and distribution of living macaques. The macaque: studies in ecology, behavior, and evolution. Edited by: Lindburg DG. 1980, New York: Van Nostrand-Reinhold, 1-9.Google Scholar
- Tosi AJ, Morales JC, Melnick DJ: Comparison of Y chromosome and mtDNA phylogenies leads to unique inferences of macaque evolutionary history. Mol Phylogenet Evol. 2000, 17: 133-144. 10.1006/mpev.2000.0834.View ArticlePubMedGoogle Scholar
- Currier JR, Stevenson KS, Kehn PJ, Zheng K, Hirsch VM, Robinson MA: Contributions of CD4+, CD8+, and CD4+CD8+ T cells to skewing within the peripheral T cell receptor beta chain repertoire of healthy macaques. Hum Immunol. 1999, 60: 209-222. 10.1016/S0198-8859(98)00109-8.View ArticlePubMedGoogle Scholar
- Lafont BA, Buckler-White A, Plishka R, Buckler C, Martin MA: Characterization of pig-tailed macaque classical MHC class I genes: implications for MHC evolution and antigen presentation in macaques. J Immunol. 2003, 171: 875-885.View ArticlePubMedGoogle Scholar
- Brennan G, Kozyrev Y, Kodama T, Hu S-L: Novel TRIM5 isoforms expressed by Macaca nemestrina. J Virol. 2007, 81: 12210-12217. 10.1128/JVI.02499-06.PubMed CentralView ArticlePubMedGoogle Scholar
- Stremlau M, Owens CM, Perron MJ, Kiessling M, Autissier P, Sodroski J: The cytoplasmic body component TRIM5alpha restricts HIV-1 infection in Old World monkeys. Nature. 2004, 427: 848-853. 10.1038/nature02343.View ArticlePubMedGoogle Scholar
- Agy MB, Frumkin LR, Corey L, Coombs RW, Wolinsky SM, Koehler J, Morton WR, Katze MG: Infection of Macaca nemestrina by human immunodeficiency virus type-1. Science. 1992, 257: 103-106. 10.1126/science.1621083.View ArticlePubMedGoogle Scholar
- Bosch ML, Schmidt A, Chen J, Florey MJ, Agy M, Morton WR: Enhanced replication of HIV-1 in vivo in pigtailed macaques (Macaca nemestrina). J Med Primatol. 2000, 29: 107-113. 10.1034/j.1600-0684.2000.290303.x.View ArticlePubMedGoogle Scholar
- Hatziioannou T, Ambrose Z, Chung NP, Piatak M, Yuan F, Trubey CM, Coalter V, Kiser R, Schneider D, Smedley J, Pung R, Gathuka M, Estes JD, Veazey RS, KewalRamani VN, Lifson JD, Bieniasz PD: A macaque model of HIV-1 infection. Proc Natl Acad Sci USA. 2009, 106: 4425-4429. 10.1073/pnas.0812587106.PubMed CentralView ArticlePubMedGoogle Scholar
- Polacino P, Larsen K, Galmin L, Suschak J, Kraft Z, Stamatatos L, Anderson D, Barnett SW, Pal R, Bost K, Bandivdekar AH, Miller CJ, Hu S-L: Differential pathogenicity of SHIVSF162P4 infection in pig-tailed and rhesus macaques. J Med Primatol. 2008, 37: 13-23. 10.1111/j.1600-0684.2008.00325.x.PubMed CentralView ArticlePubMedGoogle Scholar
- Rosenberg YJ, White BD, Papermaster SF, Zack P, Jarling PB, Eddy GA, Burke DS, Lewis MG: Variation in T-lymphocyte activation and susceptibility to SIVPBj-14-induced acute death in macaques. J Med Primatol. 1991, 20: 206-210.PubMedGoogle Scholar
- Kuller L, Schmidt A, Mack H, Durning M, Birkebak T, Reiner MT, Anderson DM, Morton WR, Agy MB: Systemic and intestinal immune responses to HIV-2287 infection in Macaca nemestrina. AIDS Res Hum Retroviruses. 2001, 17: 1191-1204. 10.1089/088922201316912790.View ArticlePubMedGoogle Scholar
- McClure J, Schmidt AM, Rey-Cuille MA, Bannink J, Misher L, Tsai CC, Anderson DM, Morton WR, Hu S-L: Derivation and characterization of a highly pathogenic isolate of human immunodeficiency virus type 2 that causes rapid CD4+ cell depletion in Macaca nemestrina. J Med Primatol. 2000, 29: 114-126. 10.1034/j.1600-0684.2000.290304.x.View ArticlePubMedGoogle Scholar
- Otten RA, Brown BG, Simon M, Lupo LD, Parekh BS, Lairmore MD, Schable CA, Schochetman G, Rayfield MA: Differential replication and pathogenic effects of HIV-1 and HIV-2 in Macaca nemestrina. AIDS. 1994, 8: 297-306.View ArticlePubMedGoogle Scholar
- Picker LJ: Immunopathogenesis of acute AIDS virus infection. Curr Opin Immunol. 2006, 18: 399-405. 10.1016/j.coi.2006.05.001.View ArticlePubMedGoogle Scholar
- Veazey RS, Marx PA, Lackner AA: The mucosal immune system: primary target for HIV infection and AIDS. Trends Immunol. 2001, 22: 626-633. 10.1016/S1471-4906(01)02039-7.View ArticlePubMedGoogle Scholar
- Douek DC, Picker LJ, Koup RA: T cell dynamics in HIV-1 infection. Annu Rev Immunol. 2003, 21: 265-304. 10.1146/annurev.immunol.21.120601.141053.View ArticlePubMedGoogle Scholar
- Kewenig S, Schneider T, Hohloch K, Lampe-Dreyer K, Ullrich R, Stolte N, Stahl-Hennig C, Kaup FJ, Stallmach A, Zeitz M: Rapid mucosal CD4+ T-cell depletion and enteropathy in simian immunodeficiency virus-infected rhesus macaques. Gastroenterology. 1999, 116: 1115-1123. 10.1016/S0016-5085(99)70014-4.View ArticlePubMedGoogle Scholar
- Lifson JD, Piatak M, Cline AN, Rossio JL, Purcell J, Pandrea I, Bischofberger N, Blanchard J, Veazey RS: Transient early post-inoculation anti-retroviral treatment facilitates controlled infection with sparing of CD4+ T cells in gut-associated lymphoid tissues in SIVmac239-infected rhesus macaques, but not resistance to rechallenge. J Med Primatol. 2003, 32: 201-210. 10.1034/j.1600-0684.2003.00026.x.View ArticlePubMedGoogle Scholar
- Mattapallil JJ, Douek DC, Hill B, Nishimura Y, Martin M, Roederer M: Massive infection and loss of memory CD4+ T cells in multiple tissues during acute SIV infection. Nature. 2005, 434: 1093-1097. 10.1038/nature03501.View ArticlePubMedGoogle Scholar
- Pandrea IV, Gautam R, Ribeiro RM, Brenchley JM, Butler IF, Pattison M, Rasmussen T, Marx PA, Silvestri G, Lackner AA, Perelson AS, Douek DC, Veazey RS, Apetrei C: Acute loss of intestinal CD4+ T cells is not predictive of simian immunodeficiency virus virulence. J Immunol. 2007, 179: 3035-3046.PubMed CentralView ArticlePubMedGoogle Scholar
- Picker LJ, Hagen SI, Lum R, Reed-Inderbitzin EF, Daly LM, Sylwester AW, Walker JM, Siess DC, Piatak M, Wang C, Allison DB, Maino VC, Lifson JD, Kodama T, Axthelm MK: Insufficient production and tissue delivery of CD4+ memory T cells in rapidly progressive simian immunodeficiency virus infection. J Exp Med. 2004, 200: 1299-1314. 10.1084/jem.20041049.PubMed CentralView ArticlePubMedGoogle Scholar
- Smit-McBride Z, Mattapallil JJ, McChesney M, Ferrick D, Dandekar S: Gastrointestinal T lymphocytes retain high potential for cytokine responses but have severe CD4+ T-cell depletion at all stages of simian immunodeficiency virus infection compared to peripheral lymphocytes. J Virol. 1998, 72: 6646-6656.PubMed CentralPubMedGoogle Scholar
- Veazey RS, DeMaria M, Chalifoux LV, Shvetz DE, Pauley DR, Knight HL, Rosenzweig M, Johnson RP, Desrosiers RC, Lackner AA: Gastrointestinal tract as a major site of CD4+ T cell depletion and viral replication in SIV infection. Science. 1998, 280: 427-431. 10.1126/science.280.5362.427.View ArticlePubMedGoogle Scholar
- Veazey RS, Mansfield KG, Tham IC, Carville AC, Shvetz DE, Forand AE, Lackner AA: Dynamics of CCR5 expression by CD4+ T cells in lymphoid tissues during simian immunodeficiency virus infection. J Virol. 2000, 74: 11001-11007. 10.1128/JVI.74.23.11001-11007.2000.PubMed CentralView ArticlePubMedGoogle Scholar
- Veazey RS, Marx PA, Lackner AA: Vaginal CD4+ T cells express high levels of CCR5 and are rapidly depleted in simian immunodeficiency virus infection. J Infect Dis. 2003, 187: 769-776. 10.1086/368386.View ArticlePubMedGoogle Scholar
- Veazey RS, Tham IC, Mansfield KG, DeMaria M, Forand AE, Shvetz DE, Chalifoux LV, Sehgal PK, Lackner AA: Identifying the target cell in primary simian immunodeficiency virus (SIV) infection: highly activated memory CD4+ T cells are rapidly eliminated in early SIV infection in vivo. J Virol. 2000, 74: 57-64. 10.1128/JVI.74.1.57-64.2000.PubMed CentralView ArticlePubMedGoogle Scholar
- Ling B, Veazey RS, Hart M, Lackner AA, Kuroda M, Pahar B, Marx PA: Early restoration of mucosal CD4 memory CCR5 T cells in the gut of SIV-infected rhesus predicts long term non-progression. AIDS. 2007, 21: 2377-2385. 10.1097/QAD.0b013e3282f08b32.View ArticlePubMedGoogle Scholar
- Pahar B, Lackner AA, Piatak M, Lifson JD, Wang X, Das A, Ling B, Montefiori DC, Veazey RS: Control of viremia and maintenance of intestinal CD4+ memory T cells in SHIV162P3 infected macaques after pathogenic SIVMAC251 challenge. Virology. 2009, 387: 273-84. 10.1016/j.virol.2009.02.014.PubMed CentralView ArticlePubMedGoogle Scholar
- Veazey RS, Acierno PM, McEvers KJ, Baumeister SH, Foster GJ, Rett MD, Newberg MH, Kuroda MJ, Williams K, Kim EY, Wolinsky SM, Rieber EP, Piatak M, Lifson JD, Montefiori DC, Brown CR, Hirsch VM, Schmitz JE: Increased loss of CCR5+ CD45RA- CD4+ T cells in CD8+ lymphocyte-depleted Simian immunodeficiency virus-infected rhesus monkeys. J Virol. 2008, 82: 5618-5630. 10.1128/JVI.02748-07.PubMed CentralView ArticlePubMedGoogle Scholar
- Paiardini M, Frank I, Pandrea I, Apetrei C, Silvestri G: Mucosal immune dysfunction in AIDS pathogenesis. AIDS Rev. 2008, 10: 36-46.PubMedGoogle Scholar
- Veazey R, Lackner A: The mucosal immune system and HIV-1 infection. AIDS Rev. 2003, 5: 245-252.PubMedGoogle Scholar
- Mattapallil JJ, Letvin NL, Roederer M: T-cell dynamics during acute SIV infection. AIDS. 2004, 18: 13-23. 10.1097/00002030-200401020-00002.View ArticlePubMedGoogle Scholar
- Harouse JM, Gettie A, Tan RC, Blanchard J, Cheng-Mayer C: Distinct pathogenic sequela in rhesus macaques infected with CCR5 or CXCR4 utilizing SHIVs. Science. 1999, 284: 816-819. 10.1126/science.284.5415.816.View ArticlePubMedGoogle Scholar
- Nishimura Y, Igarashi T, Donau OK, Buckler-White A, Buckler C, Lafont BA, Goeken RM, Goldstein S, Hirsch VM, Martin MA: Highly pathogenic SHIVs and SIVs target different CD4+ T cell subsets in rhesus monkeys, explaining their divergent clinical courses. Proc Natl Acad Sci USA. 2004, 101: 12324-12329. 10.1073/pnas.0404620101.PubMed CentralView ArticlePubMedGoogle Scholar
- Vlasak J, Ruprecht RM: AIDS vaccine development and challenge viruses: getting real. AIDS. 2006, 20: 2135-2140. 10.1097/QAD.0b013e328010beb5.View ArticlePubMedGoogle Scholar
- Harouse JM, Gettie A, Eshetu T, Tan RC, Bohm R, Blanchard J, Baskin G, Cheng-Mayer C: Mucosal transmission and induction of simian AIDS by CCR5-specific simian/human immunodeficiency virus SHIVSF162P3. J Virol. 2001, 75: 1990-1995. 10.1128/JVI.75.4.1990-1995.2001.PubMed CentralView ArticlePubMedGoogle Scholar
- Luciw PA, Pratt-Lowe E, Shaw KE, Levy JA, Cheng-Mayer C: Persistent infection of rhesus macaques with T-cell-line-tropic and macrophage-tropic clones of simian/human immunodeficiency viruses (SHIV). Proc Natl Acad Sci USA. 1995, 92: 7490-7494. 10.1073/pnas.92.16.7490.PubMed CentralView ArticlePubMedGoogle Scholar
- Pahar B, Wang X, Dufour J, Lackner AA, Veazey RS: Virus-specific T cell responses in macaques acutely infected with SHIV(sf162p3). Virology. 2007, 363: 36-47. 10.1016/j.virol.2007.01.010.PubMed CentralView ArticlePubMedGoogle Scholar
- Pal R, Taylor B, Foulke JS, Woodward R, Merges M, Praschunus R, Gibson A, Reitz M: Characterization of a simian human immunodeficiency virus encoding the envelope gene from the CCR5-tropic HIV-1 Ba-L. J Acquir Immune Defic Syndr. 2003, 33: 300-307.View ArticlePubMedGoogle Scholar
- Tan RC, Harouse JM, Gettie A, Cheng-Mayer C: In vivo adaptation of SHIV(SF162): chimeric virus expressing a NSI, CCR5-specific envelope protein. J Med Primatol. 1999, 28: 164-168.View ArticlePubMedGoogle Scholar
- Tsai L, Trunova N, Gettie A, Mohri H, Bohm R, Saifuddin M, Cheng-Mayer C: Efficient repeated low-dose intravaginal infection with X4 and R5 SHIVs in rhesus macaque: implications for HIV-1 transmission in humans. Virology. 2007, 362: 207-216. 10.1016/j.virol.2006.12.024.PubMed CentralView ArticlePubMedGoogle Scholar
- Song RJ, Chenine AL, Rasmussen RA, Ruprecht CR, Mirshahidi S, Grisson RD, Xu W, Whitney JB, Goins LM, Ong H, Li PL, Shai-Kobiler E, Wang T, McCann CM, Zhang H, Wood C, Kankasa C, Secor WE, McClure HM, Strobert E, Else JG, Ruprecht RM: Molecularly cloned SHIV-1157ipd3N4: a highly replication-competent, mucosally transmissible R5 simian-human immunodeficiency virus encoding HIV clade C env. J Virol. 2006, 80: 8729-8738. 10.1128/JVI.00558-06.PubMed CentralView ArticlePubMedGoogle Scholar
- Humbert M, Rasmussen RA, Song R, Ong H, Sharma P, Chenine AL, Kramer VG, Siddappa NB, Xu W, Else JG, Novembre FJ, Strobert E, O'Neil SP, Ruprecht RM: SHIV-1157i and passaged progeny viruses encoding R5 HIV-1 clade C env cause AIDS in rhesus monkeys. Retrovirology. 2008, 5: 94-105. 10.1186/1742-4690-5-94.PubMed CentralView ArticlePubMedGoogle Scholar
- Chen Z, Huang Y, Zhao X, Skulsky E, Lin D, Ip J, Gettie A, Ho DD: Enhanced infectivity of an R5-tropic simian/human immunodeficiency virus carrying human immunodeficiency virus type 1 subtype C envelope after serial passages in pig-tailed macaques (Macaca nemestrina). J Virol. 2000, 74: 6501-6510. 10.1128/JVI.74.14.6501-6510.2000.PubMed CentralView ArticlePubMedGoogle Scholar
- Chen Z, Zhao X, Huang Y, Gettie A, Ba L, Blanchard J, Ho DD: CD4+ lymphocytopenia in acute infection of Asian macaques by a vaginally transmissible subtype-C, CCR5-tropic Simian/Human Immunodeficiency Virus (SHIV). J Acquir Immune Defic Syndr. 2002, 30: 133-145.View ArticlePubMedGoogle Scholar
- Chase AJ, Sedaghat AR, German JR, Gama L, Zink MC, Clements JE, Siliciano RF: Severe depletion of CD4+ CD25+ regulatory T cells from the intestinal lamina propria but not peripheral blood or lymph nodes during acute simian immunodeficiency virus infection. J Virol. 2007, 81: 12748-12757. 10.1128/JVI.00841-07.PubMed CentralView ArticlePubMedGoogle Scholar
- Okoye A, Meier-Schellersheim M, Brenchley JM, Hagen SI, Walker JM, Rohankhedkar M, Lum R, Edgar JB, Planer SL, Legasse A, Sylwester AW, Piatak M, Lifson JD, Maino VC, Sodora DL, Douek DC, Axthelm MK, Grossman Z, Picker LJ: Progressive CD4+ central memory T cell decline results in CD4+ effector memory insufficiency and overt disease in chronic SIV infection. J Exp Med. 2007, 204: 2171-2185. 10.1084/jem.20070567082907c.PubMed CentralView ArticlePubMedGoogle Scholar
- Heise C, Vogel P, Miller CJ, Lackner A, Dandekar S: Distribution of SIV infection in the gastrointestinal tract of rhesus macaques at early and terminal stages of disease. J Med Primatol. 1993, 22: 187-193.PubMedGoogle Scholar
- Li Q, Duan L, Estes JD, Ma ZM, Rourke T, Wang Y, Reilly C, Carlis J, Miller CJ, Haase AT: Peak SIV replication in resting memory CD4+ T cells depletes gut lamina propria CD4+ T cells. Nature. 2005, 434: 1148-1152.PubMedGoogle Scholar
- Pandrea I, Apetrei C, Gordon S, Barbercheck J, Dufour J, Bohm R, Sumpter B, Roques P, Marx PA, Hirsch VM, Kaur A, Lackner AA, Veazey RS, Silvestri G: Paucity of CD4+CCR5+ T cells is a typical feature of natural SIV hosts. Blood. 2007, 109: 1069-1076. 10.1182/blood-2006-05-024364.PubMed CentralView ArticlePubMedGoogle Scholar
- Chun TW, Nickle DC, Justement JS, Meyers JH, Roby G, Hallahan CW, Kottilil S, Moir S, Mican JM, Mullins JI, Ward DJ, Kovacs JA, Mannon PJ, Fauci AS: Persistence of HIV in gut-associated lymphoid tissue despite long-term antiretroviral therapy. J Infect Dis. 2008, 197: 714-720. 10.1086/527324.View ArticlePubMedGoogle Scholar
- Poles MA, Boscardin WJ, Elliott J, Taing P, Fuerst MM, McGowan I, Brown S, Anton PA: Lack of decay of HIV-1 in gut-associated lymphoid tissue reservoirs in maximally suppressed individuals. J Acquir Immune Defic Syndr. 2006, 43: 65-68. 10.1097/01.qai.0000230524.71717.14.View ArticlePubMedGoogle Scholar
- Shacklett BL, Critchfield JW, Ferre AL, Hayes TL: Mucosal T-cell responses to HIV: responding at the front lines. J Intern Med. 2009, 265: 58-66. 10.1111/j.1365-2796.2008.02042.x.PubMed CentralView ArticlePubMedGoogle Scholar
- Mason RD, De Rose R, Seddiki N, Kelleher AD, Kent SJ: Low pre-infection levels and loss of central memory CD4+ T cells may predict rapid progression in SIV-infected pigtail macaques. Virology. 2008, 381: 11-15. 10.1016/j.virol.2008.08.042.View ArticlePubMedGoogle Scholar
- Siddappa NB, Song R, Kramer VG, Chenine AL, Velu V, Ong H, Rasmussen RA, Grisson RD, Wood C, Zhang H, Kankasa C, Amara RR, Else JG, Novembre FJ, Montefiori DC, Ruprecht RM: Neutralization-sensitive R5-tropic simian-human immunodeficiency virus SHIV-2873Nip, which carries env isolated from an infant with a recent HIV clade C infection. J Virol. 2009, 83: 1422-32. 10.1128/JVI.02066-08.PubMed CentralView ArticlePubMedGoogle Scholar
- Li Y, Cleveland B, Klots I, Travis B, Richardson BA, Anderson D, Montefiori D, Polacino P, Hu S-L: Removal of a single N-linked glycan in human immunodeficiency virus type 1 gp120 results in an enhanced ability to induce neutralizing antibody responses. J Virol. 2008, 82: 638-651. 10.1128/JVI.01691-07.PubMed CentralView ArticlePubMedGoogle Scholar
- Humbert M, Rasmussen RA, Ong H, Kaiser FM, Hu SL, Ruprecht RM: Inducing cross-clade neutralizing antibodies against HIV-1 by immunofocusing. PLoS ONE. 2008, 3: e3937-10.1371/journal.pone.0003937.PubMed CentralView ArticlePubMedGoogle Scholar
- Li M, Gao F, Mascola JR, Stamatatos L, Polonis VR, Koutsoukos M, Voss G, Goepfert P, Gilbert P, Greene KM, Bilska M, Kothe DL, Salazar-Gonzalez JF, Wei X, Decker JM, Hahn BH, Montefiori DC: Human immunodeficiency virus type 1 env clones from acute and early subtype B infections for standardized assessments of vaccine-elicited neutralizing antibodies. J Virol. 2005, 79: 10108-10125. 10.1128/JVI.79.16.10108-10125.2005.PubMed CentralView ArticlePubMedGoogle Scholar
- Grisson RD, Chenine AL, Yeh LY, He J, Wood C, Bhat GJ, Xu W, Kankasa C, Ruprecht RM: Infectious molecular clone of a recently transmitted pediatric human immunodeficiency virus clade C isolate from Africa: evidence of intraclade recombination. J Virol. 2004, 78: 14066-14069. 10.1128/JVI.78.24.14066-14069.2004.PubMed CentralView ArticlePubMedGoogle Scholar
- Kraft Z, Strouss K, Sutton WF, Cleveland B, Tso FY, Polacino P, Overbaugh J, Hu SL, Stamatatos L: Characterization of neutralizing antibody responses elicited by clade A envelope immunogens derived from early transmitted viruses. J Virol. 2008, 82: 5912-5921. 10.1128/JVI.00389-08.PubMed CentralView ArticlePubMedGoogle Scholar
- Wei X, Decker JM, Liu H, Zhang Z, Arani RB, Kilby JM, Saag MS, Wu X, Shaw GM, Kappes JC: Emergence of resistant human immunodeficiency virus type 1 in patients receiving fusion inhibitor (T-20) monotherapy. Agents Chemother. 2002, 46: 1896-1905. 10.1128/AAC.46.6.1896-1905.2002.View ArticleGoogle Scholar
- Polacino P, Cleveland B, Zhu Y, Kimata JT, Overbaugh J, Anderson D, Hu SL: Immunogenicity and protective efficacy of Gag/Pol/Env vaccines derived from temporal isolates of SIVmne against cognate virus challenge. J Med Primatol. 2007, 36: 254-65. 10.1111/j.1600-0684.2007.00243.x.View ArticlePubMedGoogle Scholar
- Hu SL, Zarling JM, Chinn J, Travis BM, Moran PA, Sias J, Kuller L, Morton WR, Heidecker G, Benveniste RE: Protection of macaques against simian AIDS by immunization with a recombinant vaccinia virus expressing the envelope glycoproteins of simian type D retrovirus. Proc Natl Acad Sci USA. 1989, 86: 7213-7217. 10.1073/pnas.86.18.7213.PubMed CentralView ArticlePubMedGoogle Scholar
- Blish CA, Nedellec R, Mandaliya K, Mosier DE, Overbaugh J: HIV-1 subtype A envelope variants from early in infection have variable sensitivity to neutralization and to inhibitors of viral entry. AIDS. 2007, 21: 693-702. 10.1097/QAD.0b013e32805e8727.View ArticlePubMedGoogle Scholar
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